Dynamic rotation of cathode ray tube display

ABSTRACT

A system for rotating a cathode ray display in which a signal proportional to the desired degree of rotation is applied to an auxiliary rotating coil on the display tube at a location beyond the deflection system and to a function generator providing an output signal which is applied to the display sweep circuit to compensate for non-linear variations in size of the display occasioned by the rotation thereof.

imMar-ch 13, 1973 3,341,735 9/[967 Briggs..1....1......... ............315/27GD 3,441,789 4/1969 Harrison......... ......................315/22 DYNAMIC ROTATION OF CATHODE RAY TUBE DISPLAY [75] Inventor: David E. Wadlow, Middle Barton, Primary Examiner carlD'Quarforth Engkmd Assistant ExaminerJ. M. Potenza [73] Assignee: United Aircraft Corporation, Hart- Atlor'leyaMelvin Pearson Williams ford, Conn.

[57] ABSTRACT A system for rotating a cathode ray display in which a signal proportional to the desired degree of rotation is 221 Filed: Jan. 12, 1971 Appl. No.: 105,918

applied to an auxiliary rotating coil on the display tube at a location beyond the deflection system and to a function generator providing an output signal which is applied to the display sweep circuit to compensate for 40 0H 596 127 311- ,1 v 04 m y,

l N J min c N r n a n e S L I mu UIIF 11111 2 8 555 [[l non-linear variations in size of the display occasioned by the rotation thereof.

12 Claims, 4 Drawing Figures [56] References Cited UNITED STATES PATENTS 2,829.303 4/1958 Knechtli WINS/27 GD FUNCT DYNAMIC ROTATION OF CATIIODE RAY TUBE DISPLAY BACKGROUND OF THE INVENTION It is often necessary to introduce dynamic rotation into a cathode ray tube display. For example, when the pilot of an aircraft is maneuvering it is often desirable that a display such as an artificial horizon or the like on the face of a display tube be oriented so as to remain horizontal rather than being as it would appear as a result of the maneuvering.

Various systems have been proposed in the prior art for effecting display rotation of the type described hereinabove. Some of these employ heavy mechanical rotating systems. Others employ complicated electronic circuits to achieve the required rotation.

I have invented a display rotation system for a cathode ray tube which is simpler than are systems of the prior art. My system rotates the display without appreciably affecting the character thereof. It is simple and inexpensive for the result achieved thereby. It is capable of providing a full 360 rotation in an expeditious manner.

SUMMARY OF THE INVENTION One object of my invention is to provide a dynamic cathode ray tube display rotation system.

Another object of my invention is to provide a dynamic cathode ray tube display rotation system which is simpler than are display rotation systems of the prior art.

Another object of my invention is to provide a dynamic cathode ray tube display rotation system which results in substantially no deterioration in the character of the display.

Still another object of my invention is to provide a dynamic cathode ray tube display rotation system which is capable of rotating the display through 360.

A still further object of my invention is to provide a dynamic cathode ray tube display rotation system which is less expensive than are systems of the prior art.

Other and further objects of my invention will appear from the following description.

In general my invention contemplates the provision of a dynamic cathode ray tube display rotation system in which a rotational signal is applied both to a display rotation coil on the tube downstream of the deflection system and to a function generator providing a signal which is fed to the tube sweep circuits to compensate for-non-linear changes in display size which otherwise would be introduced by rotation of the display. In one form of my system I refocus the beam and apply the rotational field to be refocused beam to minimize distortion. I may arrange my system to provide a full 360 of rotation.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings which form part of the instant specification and which are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:

FIG. 1 is a schematic view of one form of my dynamic cathode ray tube display rotation system.

FIG. 2 is a schematic view of an alternate form of my dynamic cathode ray tube display rotation system.

FIG. 3 is a diagrammatic view of the condition of components of the form of my system shown in FIG. 2 at various angles of rotation of the display.

FIG. 4 is a diagrammatic view illustrating the output of a component of the form of my system shown in FIG. 2 for various rotational displacements of the display.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 of the drawings a display tube indicated generally by the reference character 10 with which my system may be employed includes an electron gun l2, spaced vertical deflection plates 14 and spaced horizontal deflection plates 16 one of which is illustrated in the drawing. As is known in the art, the tube 10 normally provides a raster which increases in size from the deflection center of the sets of plates 14 and 16 to cover the face of the tube 18.

In my system for effecting a desired degree of rotation to the display provided by the tube 10, I place a magnetic deflection coil 20 on the neck of the tube at a point just beyond the deflection center provided by the pairs of plates 14 and 16. A signal generator 22 of any suitable type known to the art is actuated to provide an output signal which is proportional to the amount of deflection 6 desired and which has a polarity which is representative of the direction of rotation of the display. In response to the application of this signal coil 20 produces a rotation of the display proportional to the signal provided by generator 22.

As is known in the art, rotation of the display at a point slightly beyond the deflection center introduces a non-linear reduction in the size of the display. Moreover, this reduction in size is generally sinusoidal as the angle of rotation varies from zero through In order to compensate for this variation in the display size we apply the signal output from generator 22 to respective function generators 24 and 26. Respective unity gain buffer amplifiers 28 and 30 apply the signal outputs from the function generators 24 and 26 to the vertical and horizontal sweep circuits 32 and 34.

Owing to the fact that the compensation is the same for the vertical sweep as it is for the horizontal sweep I will discuss in detail only the operation of the function generator 24 associated with the vertical sweep circuit 32. As is pointed out hereinabove, the signal output from generator 22 may be either positive or negative. If the signal is negative a diode 36 applies the signal to the base of an emitter-follower transistor 38. If the signal is negative a diode 36 applies the signal to the base of an emitter-follower transistor 38. If the signal is positive it is first inverted by an inverting amplifier 40 and then is applied to the base of transistor 38 by a diode 42. It will thus be seen that either a positive or a negative input results in the application of a negative signal to the emitter follower 38. The emitter potential of the emitter follower 38 drops by a like amount to cause a pair of series-connected diodes 44 and 46 to conduct. These diodes first traverse the initial non-linear portion of their response curve and then on the linear portion thereof follow the input signal proportionally. These two diodes provide the required correction signal over approximately the first 45 of rotation of the display.

Conduction through diodes 44 and 46 changes the input signal at one terminal of a differential amplifier 48. The output of the differential amplifier thus drops to initiate conduction through a second pair of diodes 50 and 52 which provide a negative feedback to amplifier 48. Diodes 50 and 52 provide correction over the portion of the rotation from about 45 to 90'.

In the manner described above, I generate the required signal for correcting for non-linear size variation at point a. Buffer amplifier 28 applies this signal to a voltage divider including resistors 54 and 56 the common terminal of which is connected to the base of the sweep circuit charging transistor 58. This signal results in an increase in conduction through transistor 58 so that the sweep circuit capacitor 60 charges at a more rapid rate. An inverting amplifier 62 applies the capacitor signal to the vertical deflection plates of the display tube 10. A coupling capacitor 64 applies discharging pulses from a suitable source to a transistor 66 periodically to short-circuit capacitor 60 at a predetermined rate.

Referring now to FIG. 2 I have shown an alternate embodiment of my invention in which I apply a refocusing potential to a first coil 68 on tube at a point slightly beyond the deflection center of the tube so as to refocus the raster at a further distance along the tube from the deflection center thereof. In this form of my invention, I place rotating coil 70 at a point very close to the refocusing point so that the size variation introduced by the rotation is relatively small. It may, however, still be desirable to employ the function generators 24 and 26. As will be explained hereinbelow, however, the entire function generator may not be required.

I provide means for rotating the field in 90 steps so that together with the intermediate rotation provided by the coil 70 I may readily obtain 360 of rotation of the display. In order to achieve this result I apply the output of the vertical sweep circuit 32 to a first pair of switches 1S1 and 152. Similarly, I apply the output of the horizontal sweep circuit 34 to a second pair of switches 183 and 1S4. As is indicated by the linkage 72 switches 1S1 to 154 are actuated in unison by a winding 1S upon energization thereof.

I connect the respective vertical deflection plates 14 to the contact arms of respective switches 2S1 and 2S2. Similarly, the horizontal deflection plates 16 are connected to contact arms of respective switches 2S2 and 2S4. As is indicated by linkage 74 energization of winding 2S concomitantly actuates all of the switches 2S1 to 254. I so interconnect the contacts and arms of the switches associated with windings 1S and 28 that in the condition shown a normal display is provided. However, energization of winding IS with winding 28 deenergized produces 90 of rotation of the display. Energization of winding 2S with winding IS deenergized produces 180 of rotation of the display while energization of both windings provides 270 of rotation of the display.

In the arrangement shown in FIG. 2, the rotation signal generator produces 1 volt of output for each 90' of rotation. A counter 76 is adapted to be stepped so as to produce counts from one to seven. A first network 78 corresponding to plus 50 of rotation steps the counter up while a second network 80 corresponding to minus 50 of rotation steps the counter down. Thus each network 78 and 80 steps the counter at each five I ninths of a volt of a respective polarity.

The counter output actuates a digital to analog converter to produce from I to 7 volts of output which is applied to one terminal of a differential amplifier 84 the other terminal of which is connected to a source of plus four volts. The output of the differential amplifier 84 and the output of the rotation signal generator 22 are applied to the respective terminals of a second differential amplifier 86 which supplies the counter stepping networks.

Considering the situation in which 0 of rotation is desired, respective signals of O and 4 volts are applied to the terminals of network 84 so that it provides an output of 4 volts. This output, however, acts on the stepping network to step the counter to a count of four. That is the first 5/9 volt steps counter 76 to one to cause converter 82 to put out 1 volt to reduce the output of amplifier 84 to 3 volts. Then 5/9 volt again steps counter 76 to cause converter 82 to put out 2 volts to reduce the output of amplifier 84 to 2 volts. This continues until converter 82 puts out 4 volts, at which time the output of amplifier 84 is zero and no rotation of the display results.

Assuming clockwise rotation to be positive, if now it is desired to rotate the display through plus 60 for example, the rotating network 22 provides a positive signal proportional to that rotation to one terminal of network 86. At 50 however, the stepping network 78 steps the counter to a count of five to cause the converter to provide 5 volts output. Under these circumstances, amplifier 84 provides an output of plus 1 volt so that amplifier 86 produces a negative output of minus 0.4 volt. Further when counter 76 was stepped, switch 1S was energized to rotate the display through 90 thus necessitating the negative correction represented by the minus 0.4 volt.

Upon continued actuation of the generator 22 further to increase the angle of rotation in the clockwise direction counter 76 is stepped to energize winding IS and 2S successively to shift the display and then 270 in 90 steps. In FIG. 3 I have illustrated the conditions of the switches for the normal display and for the three steps of 90 shift. At the same time the counter actuates the converter 82 to provide such an output as will result in the proper signal being applied to function generators 24 and 26. In FIG. 4 I have shown the relation between the switch conditions and the output of the converter 82. Where the switch winding reference character is shown in FIG. 4 it indicates that the winding is energized. The video signal may be blanked when the switches are actuated.

From FIG. 4 it will be seen that in response to clockwise rotation the output of converter 82 successively goes from four to five to six to seven and then back to four. Operation of the system in the counter clockwise direction is analogous. The output from generator 22 for the counter clockwise direction of rotation is negative. Starting from zero with the output of converter 82 being four volts so that amplifier 84 puts out 0 volts at approximately minus 45 of rotation counter 76 will be stepped down one count so that the converter output goes to three. At this time also both windings 1S and 25 are energized. For purposes of simplicity I have outlined below the outputs of converter 82 and amplifier 84 and the condition of switch windings S1 and S2.

Rotation Gen 22 D/A/C 82 D/A84 S1 S2 3 to 405 -3.5 to -4.5 0 4 off off 225 to 3l5 2.5 to -3.5 l 3 on off l 35 to 225 1 .5 to -2.5 2 -2 off on 45 to -l35 ,0.5 to 1.5 3 -l on on --45 to +45 -().5 to 0.5 4 0 Off off +45 to 135 40.5 to +1.5 5 l on off +l35 to +225 +l.5 to +2.5 6 2 off on +225 to +3 1 5 +2.5 to +3.5 7 3 on on In the above table, as well as in FIGS. 3 and 4, l have assumed that the switching takes place at precisely 45 and at 90 intervals. This assumption ignores hysteresis in the system. Actually I may cause the switching to take place at 50 as indicated in the diagram of FIG. 2.

The operation of my system will readily be apparent from the description given hereinabove. 1n the arrangemerit illustrated in FIG. '1, as the display is rotated from zero through 90 by the application of the output of generator 22 to the coil the switch signals are modified by the function generators 24 and 26 to account for the change in size of the displays as rotation takes place. Specifically, diodes 44 and 46 account for the change over the first 45 of rotation while diodes 50 and 52 account for the change over the second 45 of rotation.

In the arrangement illustrated in FIG. 2, 1 may rotate the display over from nearly 360 by actuating the switch windings 1S and 28 to vary the plates to which the switch potentials are applied. This is done in 90 steps. At the same time by use of the counter 76 and the convertor 82 together with the amplifier 84 1 maintain the output of amplifier 86 so as to provide the required correction within the various sectors of rotation. It will be seen from the above display that for the particular arrangement I have illustrated positive rotation and correction for the error introduced thereby is possible up to 315. In the counter clockwise direction approximately 45 more than a complete revolution and correction over this rotation is possible. By slightly modifying the system 1 can accommodate as much rotation of the display as is desired.

it will be seen thatl have accomplished the objects of my invention. I have provided a dynamic cathode ray tube display rotation system. My system is appreciably simpler than are rotation systems of the prior art. It neither requires heavy mechanical equipment nor com plicated electronic arrangements. it avoids any deterioration of the display which otherwise might result from rotation thereof. It is capable of rotating the display through substantially 360. It is less expensive than are rotation systems of the prior art.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of my claims. it is further obvious that various changes may be made in details within the scope of my claims withoutdeparting from the spirit of my invention. it is, therefore, to be understood that my invention is not to be limited to the specific details shown and described.

Having thus described my invention, what I claim is:

1. 'A display rotation system including in combination, a cathode ray tube providing an axially directed electron beam, said tube comprising a beam deflection system having a deflection center, and means for providing an axially directed magnetic field in a region downstream of'said deflection center.

2. A system as inclaim l in which said field providing means is a coil surrounding said tube.

3. A system as in claim 1 in which said deflection system comprises a source of a beam deflecting signal and means responsive to said field producing means for modifying said deflection signal to compensate for variation in said display resulting from said field.

4. A system as in claim 1 in which said deflection system comprises a source of a beam deflecting signal, said system including a non-linear function generator, means responsive to said field producing means for actuating said generator to produce an output signal, and means for applying said output signal to said deflection signal source to compensate for variation in said display resulting from said field.

5. A system as in claim 1 in which said deflection H a.

system comprises a source of a horizontal deflection signal and a source of a vertical deflection signal, said system including respective non-linear function generators, means responsive to said field producing means for actuating said function generators to produce respective output signals, and means for applying said output signals to said deflection signal sources.

6. A system as in claim 1 in which said deflection system respective first and second deflection signal sources and respective first and second beam deflecting means operating on orthogonal axes, switching means for selectively applying said deflection signals respec tively to said deflecting means, said field producing means comprising a source of a display rotating signal and means responsive to said display rotating signal for actuating said switching means to rotate said beam through 7. A cathode ray tube display rotation system including in combination, a cathode ray tube having a display screen, a source of an electron beam, respective first and second electron beam deflecting means arranged to deflect said beam with respect to orthogonal axes, respective first and second deflection signal sources, means for applying said deflection signals to said deflecting means to cause said electron beam to form a display on said screen, a source of display rotating voltage, auxiliary means on said tube adapted to be energized to rotate said display means for applying said rotating signal to said auxiliary means, respective nonlinear function generators for producing correction signals, means for applying said rotating signal to said non-linear networks and means for applying said correction signals to said deflection signal sources to compensate for variation in said display resulting'from said rotation.

8. A system as in claim 7 in which said means for applying said deflection signals to said deflection means comprises switching means adapted to be actuated to shift said display through approximately 90 and means responsive to said rotating signal for actuating said switching means to shift said display.

9. Apparatus as in claim 8 including means responsive to said rotating signal for actuating said switching means to shift said display through in 90 steps.

10. Apparatus as in claim 8 including means responsive to said switch actuating means for modifying the input to said non-linear generators as said display is shifted 90.

11. Apparatus as in claim 7 including means on said tube beyond said deflection center for refocusing said beam at a location beyond said refocusing means, and

positioned downstream of said deflection center and having a focus at a point downstream from said deflection center, and means for providing an axially directed magnetic field in a region including said focal point. 

1. A display rotation system including in combination, a cathode ray tube providing an axially directed electron beam, said tube comprising a beam deflection system having a deflection center, and means for providing an axially directed magnetic field in a region downstream of said deflection center.
 1. A display rotation system including in combination, a cathode ray tube providing an axially directed electron beam, said tube comprising a beam deflection system having a deflection center, and means for providing an axially directed magnetic field in a region downstream of said deflection center.
 2. A system as in claim 1 in which said field providing means is a coil surrounding said tube.
 3. A system as in claim 1 in which said deflection system comprises a source of a beam deflecting signal and means responsive to said field producing means for modifying said deflection signal to compensate for variation in said display resulting from said field.
 4. A system as in claim 1 in which said deflection system comprises a source of a beam deflecting signal, said system including a non-linear function generator, means responsive to said field producing means for actuating said generator to produce an output signal, and means for applying said output signal to said deflection signal source to compensate for variation in said display resulting from said field.
 5. A system as in claim 1 in which said deflection system comprises a source of a horizontal deflection signal and a source of a vertical deflection signal, said system including respective non-linear function generators, means responsive to said field producing means for actuating said function generators to produce respective output signals, and means for applying said output signals to said Deflection signal sources.
 6. A system as in claim 1 in which said deflection system respective first and second deflection signal sources and respective first and second beam deflecting means operating on orthogonal axes, switching means for selectively applying said deflection signals respectively to said deflecting means, said field producing means comprising a source of a display rotating signal and means responsive to said display rotating signal for actuating said switching means to rotate said beam through 90*.
 7. A cathode ray tube display rotation system including in combination, a cathode ray tube having a display screen, a source of an electron beam, respective first and second electron beam deflecting means arranged to deflect said beam with respect to orthogonal axes, respective first and second deflection signal sources, means for applying said deflection signals to said deflecting means to cause said electron beam to form a display on said screen, a source of display rotating voltage, auxiliary means on said tube adapted to be energized to rotate said display means for applying said rotating signal to said auxiliary means, respective non-linear function generators for producing correction signals, means for applying said rotating signal to said non-linear networks and means for applying said correction signals to said deflection signal sources to compensate for variation in said display resulting from said rotation.
 8. A system as in claim 7 in which said means for applying said deflection signals to said deflection means comprises switching means adapted to be actuated to shift said display through approximately 90* and means responsive to said rotating signal for actuating said switching means to shift said display.
 9. Apparatus as in claim 8 including means responsive to said rotating signal for actuating said switching means to shift said display through 180* in 90* steps.
 10. Apparatus as in claim 8 including means responsive to said switch actuating means for modifying the input to said non-linear generators as said display is shifted 90*.
 11. Apparatus as in claim 7 including means on said tube beyond said deflection center for refocusing said beam at a location beyond said refocusing means, and means positioning said auxiliary means adjacent to said location. 